Is this the official installation or from some manufacturer? Our version calls by default only our servers and linux might call nearest timeserver to update clock or linux update server to check for updates.
It is possible to configure it to contact others, eg. manufacturer might have a own update server they check instead.
We can work offline except for activating/deactivating license and checking updates/updating. Timeserver should not be blocked on pi because pi forgets time after power off and needs it to set correct time. Without https will not work correctly and timestamps are wrong but all should work for printing.
